Malaysia Airlines 777-200, en route to Beijing from Kuala Lumpur, vanished suddenly from radar screens early Saturday morning. What could have happened? As the search enters its fifth day, investigators and the public alike are questioning how a modern jetliner could disappear with so few clues to its whereabouts or to the causes of its apparent demise. “Planes don’t just fall out of the sky,” was the phrase repeated frequently by pundits after flight 370, carrying 239 people, went missing 40 minutes after leaving Kuala Lumpur. But that misses the point. The presumption seems to be that an omniscient surveillance system in the sky must know the exact position of every commercial airliner at all times. As aviation insiders know well, that’s far from the case.

Current air traffic surveillance worldwide is a patchwork of conventional radar and satellite coverage that can have wide gaps in coverage. In fact, the mystery over what did happen to the plane is drawing some needed attention to the deficiencies in how planes are tracked, just as the search for the ‘black box’ recorders—which capture a flight’s last moments—is casting doubts on the efficacy of this piece of 1960s-era technology.

In this day of ubiquitous GPS tracking, from the family car to your iPhone, it strikes laymen as implausible that something like a giant airliner could not be found immediately. But it is in fact possible for a plane to drop from sight, however briefly, even on a routine trip.

What we do know is this: The last people known to have any contact with the ill-fated Malaysia flight 370 were the air traffic controllers working the night shift in Subang, Malaysia. And when the blip identifying the 777-200 dropped from their screens, it produced one of the few scraps of real evidence that something went terribly wrong. There was no warning from the cockpit, no Mayday call. That suggests a catastrophic event—for instance, the plane could have disintegrated at cruising altitude, 35,000 feet, which will complicate discovery even further, since the debris would be spread over a vast area. (Already, other sea debris has raised false alarms: An object thought to be a jet door disappeared before it could be verified, and the oil slick originally thought to be proof of a crash turned out to be cargo ship fuel.)

In another high profile mid-air accident, Air France 447, in June of 2009, lapses in communication among control centers over the Atlantic led to delays in declaring an emergency. Then a futile search for the black boxes (which as my colleague Clive Irving points out, are neither black nor a box) ran out of steam; after several deep sea searches over the next two years, the data boxes were found at the bottom of a trench at a depth of 13,000 feet. That spurred aviation safety regulators to push for more redundancies in the recorder system, with the goal of ultimately moving to a continuous satellite link that would transmit data in real time, to be captured instantly in the event of a crash. The cause of the Air France accident ultimately was pinned on a series of glitches, starting with the gauges that measure speed; the pilots’ failure to respond appropriately to repeated stall warnings was also blamed. But all of that would have been much clearer if the black box data were available immediately.

Even so, no plan was made to move to this system. Why not? Despite the long and very expensive Air France probe, complacency set in, and airlines opted to spend their tech dollars on fancy inflight entertainment systems instead—especially on the long-distance jetliners capable of making overwater flights.

The race is now on to find the recorders—whose battery life is only guaranteed for 30 days. That artificial deadline would be irrelevant if the new streaming system were in place.

Barbara Peterson appeared on public radio's The Takeaway this morning, discussing the disappearance of MH370.